The objective of this research project is to define the role of enterotoxigenic strain of Escherichia coli in human diarrheal disease because of the development of a tissue culture system for the more sensitive and rapid detection of heat-labile, cholera-like, E. coli enterotoxins and antibodies to these toxins, realization of the stated objective should be more feasible. Previous methodology has depended on the use of cumbersome and often unreliable animal intestinal-loop model systems and serological identification of the predominant E. coli organism recovered during outbreaks of diarrhea; the latter not being an accurate method for the detection of enterotoxigenic strains. The adrenal cell tissue culture system to be used in these studies responds to the heat-labile E. coli enterotoxins by undergoing cellular morphologic and steroidogenic changes, either or both of which assay parameters can be used for detection of enterotoxin or antitoxin. What we propose to do is to conduct a series of seroepidemiologic surveys in order to determine the prevalence of E. coli antitoxin in demographically-defined populations, then to initiate prospective studies in which acute and convalescent stools would be examined for enterotoxin and toxigenic strains of E. coli and in which acute and convalescent sera from individuals affected with diarrhea would be tested for their content of antitoxin. Thus, these studies would furnish valuable information on the role of these toxigenic E. coli strains in human diarrheal disease. An additionl objective of this reseach project is to develop a tissue culture model system for assay of the heat-stable toxin (ST) of E. coli. Should this goal be realized, similar seroepidemiologic and prospective studies as that proposed for the heat-labile toxin could be conducted with ST. As there is no current evidence to suggest that ST is immunogenic, these seroepidemiologic studies may not be possible; should the development of a tissue culture model for ST not be successful, we my have to rely on the infant-mouse mode for the assessment of any ST producing strains of E. coli.